This invention relates to water pumps for marine propulsion devices, and more particularly to the impeller-drive shaft assembly of such a water pump.
Water pumps in marine propulsion devices typically have rubber vaned impellers that are eccentrically located in the pump chamber. Such an impeller is inherently unevenly loaded, and this causes a wearing action between the impeller assembly and the drive shaft with each rotation.
This wearing action necessitates the impeller assembly's having an inner member which receives the drive shaft and is made of strong, wear-resistant material, and an outer impeller member having a rubber vaned portion. The inner member is usually molded and/or bonded to the outer impeller member and is typically made of bronze, stainless steel, or other corrosive-resistant materials.
A common practice is to adhesively bond the inner member to the rubber outer member during the molding process. In operation this adhesive bond can break down and allow the inner member to rotate relative to the outer member, rendering the water pump inoperable.
Typical means for the driving of the impeller assembly by the drive shaft are a woodruff key and slot, spline joints, and drive pins, for example. With extended operation, the wearing action between these drive mechanisms and the inner member can cause damage to either member and can ultimately result in failure of the water pump.
Attention is directed to the following U.S. patents which disclose pump impeller-shaft assemblies.
______________________________________ Patentee U.S. Pat. No. Issued ______________________________________ Klein 2,070,738 Feb. 16, 1937 Mayus 2,663,263 Dec. 22, 1953 Doble 2,892,646 June 30, 1959 Bandli 2,899,902 Aug. 18, 1959 McLean 2,971,469 Feb. 14, 1961 Swanson 3,097,610 July 16, 1963 Kramer 3,113,527 Dec. 10, 1963 ______________________________________